I have had stalls on very long fasts. My wonderful naturopath/nutritionist assures me the body is working hard on other issues and will get back to burning fat in its good time, and I have found this true.
DO try adding exercse--I walk 40 minutes a day during fasts, barring crises.
And that cleansing diet post-fast DOES continue to take the weight off, slowly but surely in my experience. I ate that way for six months after my 60 day fast last summer and continued to lose.